1. Technical Field
Embodiments of the present disclosure relate to a voltage generator, and more particularly, to a high voltage generator receiving an external voltage and generating a voltage higher than the external voltage.
2. Related Art
A flash memory device used for, e.g., a universal serial bus (USB) storage device or a solid state disk or solid state drive (SSD) storage device, uses a high voltage as a pass voltage or as a program voltage during its operation. Moreover, other electronic devices including display drivers may use a high voltage during their operation.
FIG. 1 is a block diagram illustrating a conventional high voltage generator. The conventional voltage generator includes a first charge pumping device 10 configured to generate a first output voltage higher than an external source voltage VCCE, and a second charge pumping device 20 configured to generate a second output voltage higher than the first output voltage output from the first charge pumping device 10.
Each of the first charge pumping device 10 and the second charge pumping device 20 includes a plurality of unit pumps 1. Each unit pump 1 is driven by the external source voltage VCCE. Detailed descriptions of the configuration and operation of the unit pump 1 are omitted herein for illustrative convenience since the configuration and operation of a conventional unit pump 1 is well-known to those skilled in the art.
The conventional high voltage generator further includes a first regulator 30 configured to output a pass voltage VPASS by regulating the first output voltage of the first charge pumping device 10, and a second regulator 40 configured to output a program voltage VPROG by regulating the second output voltage of the second charge pumping device 20. The high voltage generator may generate a pass voltage VPASS in the range of 8˜9 V and a program voltage VPROG in the range of 20˜25 V using an external source voltage VCCE of 3.3 V.
The conventional high voltage generator uses a plurality of charge pumping devices, e.g., 10 and 20, connected in series and each of the charge pumping devices 10 and 20 includes a plurality of unit pumps. As a result, it is difficult to reduce a circuit area and increase power efficiency.